SfePy December 2016

sfepy@python.org

5 participants
12 discussions

Material Parameters of Individual Nodes
by derj...＠web.de 12 Apr '22

12 Apr '22

Hello! It's a great tool you built there! I'd like to use it for some kind of topology optimisation. Is there an "idiomatic" way to set the material parameters of individual nodes? Thank you very much! JonnyB

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Calculate total force from cauchy stress
by Patricia Garcia Cañadilla 17 Jan '19

17 Jan '19

Dear Robert, I have a 2D body of hyperelastic material which contracts and I would like to compute the total force developed by the body from the cauchy stress. I am trying to follow some of your indications I found in this group, but I still couldn't make it works. Could you please help me to fix the problem? I am getting the following error: key = (region.name, integral.order, integration) AttributeError: 'dict' object has no attribute 'name' I am trying to do the following, inside stress_strain post-processing function: def stress_strain(out, problem, state, extend = False ): from sfepy.base.base import Struct from sfepy.mechanics.tensors import StressTransform from sfepy.mechanics.tensors import transform_data from sfepy.discrete.common.mappings import get_normals ev = problem.evaluate field = problem.fields['displacement'] region = problem.domain.regions['Gamma'] integral = problem.integrals['i2'] n = get_normals(field,integral,regions) stress = ev('dw_tl_fib_a.1.Omega(f1.fmax, f1.eps_opt, f1.s, f1.fdir, f1.act, v, u )',mode='qp', term_mode= 'stress'); F = ev('ev_def_grad.1.Omega(u)',mode='el_avg'); transform = StressTransform(F) Cstress = transform.get_cauchy_from_2pk(stress) T = Cstress*n; Force = ev('ev_surface_integrate.2.Gamma(T)') And here it is part of the problem configuration file. fields = { 'displacement': ('real', 'vector', 'Omega', 1), } materials = { 'solid' : (None, 'get_elastic_pars'), 'load' : (None, 'linear_tension'), 'f1' : 'get_pars_fibres1', } variables = { 'u': ('unknown field', 'displacement', 0), 'v': ('test field', 'displacement', 'u'), } regions = { 'Omega' : 'all', 'Fix1' : ('vertices in x < %.10f' % (fix_point + eps2), 'facet'), 'Fix2' : ('vertices in x > %.10f' % (fix_point - eps2), 'facet'), 'Fix' : ('r.Fix1 *v r.Fix2', 'facet'), 'Gamma' : ('vertices of surface','edge'), } ebcs = { 'fixb' : ('Fix', {'u.all' : 0.0}), } integrals = { 'i1' : ('v', 1), 'i2' : ('s', 2), }

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Re: Torque
by Robert Cimrman 09 Mar '18

09 Mar '18

In examples/large_deformation/hyperelastic.py a rotation by displacements is applied. By using a similar function the vectors defining the force couples could be defined for dw_surface_ltr (IMHO). Does it make sense? r. ----- Reply message ----- From: "Andre Smit" <freev...(a)gmail.com> To: <sfepy...(a)googlegroups.com> Subject: Torque Date: Sat, Dec 18, 2010 05:10 What is the best way to apply a torque load to a model? -- Andre -- You received this message because you are subscribed to the Google Groups "sfepy-devel" group. To post to this group, send email to sfepy...(a)googlegroups.com. To unsubscribe from this group, send email to sfepy-devel...(a)googlegroups.com. For more options, visit this group at http://groups.google.com/group/sfepy-devel?hl=en.

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new interactive example with time stepping
by Robert Cimrman 13 Mar '17

13 Mar '17

Hi, I have just updated the time stepping solvers in sfepy for interactive use, as demonstrated in the new example [1]. For basic use, ignore the probing code - the time stepper can be used as simply as: tss = SimpleTimeSteppingSolver({'t0' : 0.0, 't1' : 100.0, 'n_step' : 11}, problem=problem) tss.init_time() for step, time, state in tss(): pass r. [1] http://sfepy.org/doc-devel/examples/diffusion/time_poisson_interactive.html

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one problem in ''biot.py"
by Kid Guo 10 Jan '17

10 Jan '17

Hi, I have a problem based on "../sfepy/examples/multi_physics/biot.py". In the attached scripy 'block2.py', I have calculated the stress and strain according to the displacement, at the 111 and 112 lines you can see it. Now I want to output the K of every cell, I gave a value of k at the 64 line in this script, it is a 3*3 array. I don't know which function or equation to use, so I was stucked at the 113 line. if I change the K value, will where be some difference results? Thank you advance K.

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Correct unit in linear volume force term
by Radko Bankras 29 Dec '16

29 Dec '16

Hi, My mesh is defined in mm. With units = ['mm', 's', 'kg', 'C'] the matching units for density and force are Tg/m**3 and mNewton, respectively. I would like to determine the linear elastic displacement of the meshed object by gravity, using the linear volume force term t2 = Term.new('dw_volume_lvf(f.val, v)', integral, omega, f=f, v=v) in which the force vector f.val is obtained from function get_gravity. def get_gravity(ts, coors, mode=None, equations=None, term=None, problem=None, **kwargs): if mode == 'qp': # define material parameters in quadrature points fx = nm.zeros((coors.shape[0], 1, 1)) fy = nm.zeros((coors.shape[0], 1, 1)) fz = nm.tile(-2.285e-2, (coors.shape[0], 1, 1)) # constant vertical force in mN/mm3 val = nm.concatenate((fx, fy, fz), axis=1) # concatenate force components return {'val': val} With gravity g = 9.81 m/s**2 and density rho = 2.329e-6 Tg/m**3, the constant volume force 2.285e-2 mNewton/mm**3 is obtained as the product of gravity and density. Is it correct that f.val in the linear volume force term is defined in force per unit volume? And another newbie question: Is it correct that a first order integral is used for the linear volume force term, because of the linear relation between force and volume? Or is a higher integral order needed, due to the dimensions of the mesh? Kind regards, Radko

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Vector decomposition of ev_cauchy_strain
by Radko Bankras 28 Dec '16

28 Dec '16

Hi, The following code is used in example linear_elasticity/material_nonlinearity.py to evaluate the Cauchy strain during post processing: strain = problem.evaluate('ev_cauchy_strain.i.Omega(u)', mode='el_avg') out['cauchy_strain'] = Struct(name='output_data', mode='cell', data=strain, dofs=None) Using ParaView to visualize the result on a tetrahedral mesh from VTK output, I find the strain to have 8 decomposition components with arbitrary names 1 through 8. Is it possible to obtain the strain as a vector in Cartesian components? Regards, Radko

2 3

Passing function values in interactive mode
by David Jessop 21 Dec '16

21 Dec '16

Hi, I'm trying to solve a non-linear Poisson type equation where the diffusion coefficient/conductivity depends on the field variable. Logically, I've tried basing this part of my code on the poisson_field_dependent_material.py case and, of course, it works nicely in "simple" mode but I can't figure out how to pass the value to my material variable "cond" in interactive mode (I require interactive mode for reasons stated in this post <https://groups.google.com/forum/#!topic/sfepy-devel/es64x4YFEiU>). I define the same get_conductivity function as per poisson_field_dependent_material.py, then declare the function as conductivity_fun = Function('conductivity_fun', get_conductivity) get_conductivity returns a dictionary key/value pair {'val' : val} so I figured to call the function as per cond = Material('cond', conductivity_fun) should work, but it results in this error: Traceback (most recent call last): File "examples/diffusion/myPoisson/myPoissonInteractive.py", line 185, in <module> main() File "examples/diffusion/myPoisson/myPoissonInteractive.py", line 116, in main cond = Material('cond', conductivity_fun,) #val= 2.0) File "/usr/local/lib/python2.7/dist-packages/sfepy-2016.3_git_94dff5a051dbd2bf6bd56fce936d75878edef9e8-py2.7-linux-x86_64.egg/sfepy/discrete/materials.py" , line 148, in __init__ % self.name TypeError: not enough arguments for format string I've also tried passing a function handle to cond ('conductivity_fun'), and all the possible combinations of function names that I can think of, but this error persists. I've looked at the function documentation <http://sfepy.org/doc-devel/users_guide.html#functions> but unfortunately this hasn't clarified things for me as this issue pertains specifically to the interactive problem specification. Thank you for your help. Regards, David

2 1

specifying an initial guess for non-linear problems with no ebcs
by David Jessop 21 Dec '16

21 Dec '16

<https://lh3.googleusercontent.com/-nqPKBodss14/WEbGCb-rgXI/AAAAAAAAA70/sQ8d…> Hi, I have a non-linear form of the Poisson equation where the "diffusion" coefficient depends on the derivatives of the state variable (see image). There are no Dirichlet-type boundary conditions (i.e. no ebcs) so I really need to specify a good initial guess at the solution. My questions are: 1) How are initial guesses passed to the solver? From the documentation, it doesn't seem like initial guesses can be directly passed to the nls.newton solver as an argument (though they are an argument of the subroutine __call__). 2) In what form should the initial guess vector/array be written? Can a function be passed? Do numerical values have be be specified at the mesh nodes? Thanks for any help on this matter. D

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errors when running ipython --profile=sfepy
by silesa...＠hotmail.com 16 Dec '16

16 Dec '16

Hello, I have created an ipython profile for sfepy, i have edited the file ~/.ipython/profile_sfepy/ipython_config.py addinging the suggested lines in the installation manual. My system is Fedora 24 Igot the following errors: IPython profile: sfepy --------------------------------------------------------------------------- ImportError Traceback (most recent call last) <ipython-input-1-3df2942fcc0c> in <module>() ----> 1 from sfepy.base.base import * ImportError: No module named sfepy.base.base --------------------------------------------------------------------------- ImportError Traceback (most recent call last) <ipython-input-1-7107ce501ecc> in <module>() ----> 1 from sfepy.discrete import * ImportError: No module named sfepy.discrete --------------------------------------------------------------------------- ImportError Traceback (most recent call last) <ipython-input-1-4cb6370fc83c> in <module>() ----> 1 from sfepy.discrete.fem import * ImportError: No module named sfepy.discrete.fem --------------------------------------------------------------------------- ImportError Traceback (most recent call last) <ipython-input-1-774ff483fc4b> in <module>() ----> 1 from sfepy.applications import solve_pde ImportError: No module named sfepy.applications Is it possible to correct those errors? I'll appreciate any help. Hugo

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SfePy December 2016